Muscular System

My muscles are important because they… Hold my organs in place Hold my bones together so that I can move Help me chew my food Open and close my eyelids Pump my blood Allow me to run and play Help me to smile!

What are muscles made of? Stretchy, elastic cells and fibers What else is stretchy like a muscle?

Did you know that ? more than 50% of body weight is muscle ! more then 60% of your body heat is generated by muscle contractions – maintain body temperature -You have over 650 muscles -It takes more muscles to frown then it does to smile

Three types of muscle Skeletal Cardiac Smooth

Classification of muscle Voluntary – choice to contract Involuntary – contracts automatically Skeletal Cardiac Smooth Limbs Heart Viscera organs Striated- look striped Non-striated – not striped Note: Control, Location and Structure

Skeletal muscle Large muscles Maintain posture Facilitate locomotion – PULL ON BONES Move jointed bones Found in antagonistic pairs Attached to bones by tendons

Structure of skeletal muscle Each cell (fibre) is long and cylindrical Muscle fibres are multi-nucleated = more then one nucleus Have large number of mitochondria = organelle that produces ATP (energy)

Skeletal muscle - Summary Voluntary movement of skeletal parts Spans joints and attached to skeleton Multi-nucleated, striated, cylindrical fibres

Cardiac muscle Main muscle of heart Pumping mass of heart Critical To Life Heart muscle cells behave as one unit Heart always contracts to it’s full extent

Structure of Cardiac Muscle Cells (fibres) are short, branched and interconnected striated & multi-nucleated Adjacent cells joined via electrical synapses (gap junctions)

Cardiac muscle - Summary Found in the heart Involuntary rhythmic contraction Branched, striated fibre with single nucleus and intercalated discs

Smooth muscle Lines walls of viscera (organs) Found in longitudinal or circular arrangement Alternating contractions of muscles in the digestive system leads to peristalsis

Structure of Smooth Muscle Cells uni-nucleated (one nucleus) cells Striations not observed Actin and myosin filaments are present Ratio of thin-to-thick filaments is 16:1 (in striated muscle this is 2:1) Myosin filaments are attached to dense bodies at the end of each cell

Smooth muscle - Summary Found in walls of hollow internal organs Involuntary movement of internal organs Elongated, spindle shaped fibre with single nucleus

Muscle Control Type of muscle Nervous control Type of control Example Skeletal Controlled by CNS Voluntary Lifting a glass Skeletal Cardiac Regulated by ANS Involuntary Heart beating Smooth Controlled by ANS Involuntary Peristalsis